RomRaider

While scratching around in the ROM sorting out the RomRaider CAN bus logging update I came across the fuel efficiency calculation routine. This routine calculates a uint16 value which is then sent out on the CAN bus to the Combination Meter. The Combination Meter uses this info plus Vehicle Speed from the ABS/VDC and remaining fuel from the BIU to calculate Instant fuel efficiency, Average fuel efficiency and Remaining travel distance to be displayed in the Driver Information Panel.

This definition will be important to people who have changed their fuel injectors to a non-stock size as the injector pulse width is a key component in the fuel efficiency calculation.

When the injectors are changed out for large capacity injectors the pulse width shortens for the same fuel quantity delivered. The shorter pulse width is erroneously translated into better fuel efficiency by the ECU. To use this correction definition you will most likely be increasing the value from stock. There's two approaches which can be used to determine a starting correction, which can be fine tuned later.

1. You can use the change in injector size to determine a correction to apply.
   First, obtain the Injector Flow Scaling for your stock ROM as displayed by RomRaider. Then obtain the Injector Flow Scaling for your modified ROM as displayed by RomRaider. Calculate the correction as follows:
   Injector Flow Scaling Modified / Injector Flow Scaling Stock = correction
   
2. An alternate method to determine the correction which may work better for people using high Ethanol fuel blends is to calculate your fuel consumption in the traditional manner. Which is to reset the trip meter, fill the tank and drive until at least half a tank of fuel is consumed, refill the tank and calculate your consumption over that distance. Then compare this to the Driver Information Panel Average Fuel Efficiency value. Calculate the correction as follows:
   Fuel Efficiency Calculated / Info Panel Average Fuel Efficiency = correction

With this correction value in hand you can apply it to the 'EXPERIMENTAL Info Panel Fuel Efficiency Correction' in the 'Fueling - Injectors' category as defined by the following definition update.

To apply this update to your ROM, search for your CAL ID in the RomRaider ECU definition XML file using a text editor. If you find your CAL ID inherits from a previous CAL ID then apply this update to the inherited CAL ID. Once you locate the CAL ID, scan down the definition until you locate the table entry for name="Injector Flow Scaling". After this line insert the following code:
Once you have inserted the code change the value of the parameter storageaddress="0x#####" and replace the ##### with the address value defined for your CAL ID. Save the XML file.

Open your modified ROM and open the table 'EXPERIMENTAL Info Panel Fuel Efficiency Correction' in the 'Fueling - Injectors' category. Select the current value and enter the correction you calculated in the table modify field. Click the 'Mul' button. Save the ROM and flash the update to the ECU.
This initial correction should get the readings closer to reality. Adjust the 'EXPERIMENTAL Info Panel Fuel Efficiency Correction' as required to obtain the best realistic result after a few tanks of fuel.

storageaddress="0x#####" by CAL ID:
A2TB001L: C17AC
A2UG000L: C17AC
A2UG001G: C1850
A2UG002T: C1850
A2UI000Y: C1854
A2UI000Z: C1854
A2WC510N: C141C
A2WC521N: C1428
A2WC521S: C1428
A2WC522N: C1428
A2WC522S: C1428
A2WD002T: 62838
A2WF200C: C1428
A2ZJD02G: 5EF84
AE5I910L: C14BC
AE5I910V: C1200
AE5IB00L: C14BC
AE5IB00V: C1200
AE5K500V: C1214
AE5K611L: C14D0
AE5K611V: C1214
AZ1E400C: C10C8
AZ1G101M: C10CC
AZ1G101N: C10CC
AZ1G201G: C0E14
AZ1G202G: C0E14
AZ1G202I: C0C54
AZ1G300F: C10EC
AZ1G400W: C10CC
AZ1G700J: C0E18
AZ1G800D: C10D0
AZ1G800F: C0ED8
AZ1G800S: C10F0
AZ1G800T: C1188
AZ1G800V: C1170
AZ1G900C: C10D0
AZ1G900O: C10D0
AZ1G900P: C10D0
AZ1J500G: C0E1C
AZ1J500J: C0EE0
AZ1J500V: C10D8
D0XJ001M: C07F8
D0XJ001T: C07F8
D2UH001M: C0808
D2UH001T: C0808
D2UJ001M: C0808
D2UJ001T: C0808
D2WD603H: 72D48

I have been using this since April 17 and my fuel consumption gauge is now spot on. I had to calibrate mine twice as I was on e85. First was for the computed multiplier (new injector/old injector). 2nd time, I ensured I had it stop at automatic at full tank. When I was almost at empty, refilled again at the same pump up to automatic stop only. Computed for actual FC 100/(kilometers driven/liters of fuel). I divided this with what my fc gauge displayed and multiplied it with the fuel efficiency correction value.

Im using ID 1000cc on e85 using a scalar of 662.46. My fuel correction efficiency value is 13.810
My friend Raymond is on ID 1000cc and using Petrol, scalar of 890. His actual fuel correction is 14.756

Thanks Dale for finding this table, been searching for this a long time now
http://legacygt.com/forums/showthread.php/fuel-economy-meter-now-inaccurate-116657.html
viewtopic.php?f=15&t=6033

AE5IB00V and all above posted to github: https://github.com/Merp/SubaruDefs/commits/Alpha

AZ1G101M, AZ1G900P,AZ1G900C,AZ1J500J, and AE5I910V all pushed to git.

Throttlehappy, if you upload the AZ1J500V ECUFlash def to the thread I'll add this table and push it.

First post updated with recent requests.

Thanks for ecuflash conversion

Can confirm that E85 uses the normal injector size change, so ID1000's upgraded from 550's is around a 1.84 multiplier. Injector size change for E85 obviously alters the pulsewidth anyway

I would love to use this for a 2008 STi, CAL ID AZ1G202I. I tried the 202G and a zero is at that location so I'm pretty sure it's wrong. Can anyone give me pointers on how to find it? Reference the same difference from another table?

C0C54

Thanks so much!

I think AE5I910L is C14BC. That's the only address I can find with 9.0249996 in it.

Yes it is.

A2WD002T

<table name="Info Panel Fuel Consumption Correction" category="Fuel" address="62838" type="2D" level="1" scaling="rawecuvalue">
<description>This is the correction applied to the fuel efficiency calculation to account for injector size change. Adjust this value by the same percentage as used for injector scaling. NewCorrection = CurrentCorrection * (NewInjectorScale / OldInjectorScale)</description>
<table name="Fuel Efficiency Correction" type="Static Y Axis" elements="1">
<data>Value</data>
</table>
</table>

I'm not really sure what I did wrong, but as of right now I am seeing ZERO change in my mpg average on the display. I tried using the calculations multiple times, and when they didn't work, I plugged in huge numbers just to see of they would make a difference. I currently have 56.00 in there and am still getting 27mpg on e85 according to the gauge but an actual calculation of closer to 17mpg. Maybe I am just not waiting long enough for it to correct...how long does it take to actually start showing the effect? I assumed it would be pretty instant since it is reading raw ecu data...